The present invention relates to seals for gas turbine engines and, more particularly, to an air leakage seal for the blade root region of a compressor rotor blade.
Gas turbine engines have been utilized to power a wide variety of vehicles and have found particular application in aircraft. The operation of a gas turbine engine can be summarized in a three step process in which air is compressed in a rotating compressor, heated in a combustion chamber, and expanded through a turbine. The power output of the turbine is utilized to drive the compressor and any mechanical load connected to the drive. Modern lightweight aircraft engines, in particular, have adopted the construction of an axial-flow compressor comprising a plurality of lightweight annular disk members carrying airfoils at the peripheries thereof. Some of the disk members are attached to an inner rotor and are therefore rotating (rotor) blade assemblies while other disk members depend from an outer casing and are therefore stationary (stator) blade or vane assemblies. The airfoils or blades act upon the fluid (air) entering the inlet of the compressor and raise its temperature and pressure preparatory to directing the air to a continuous flow combustion system. The air travels through a flowpath which traverses several stages of rotor blades and stator vanes.
As air is directed downstream across a compressor rotor blade, a rise in pressure occurs. This pressure differential between the downstream side of the rotor blade and its upstream side creates an opportunity for air to leak back upstream through any root attachment gaps. These gaps can be blade-to-blade, i.e., those gaps existing between rotor blades in a given stage, and/or blade-to-disk, i.e., those gaps existing between a blade and the rotor disk to which it is attached.
The sealing of such blade-to-blade and blade-to-disk gaps has proved to be a difficult problem to address. Some of these gaps have been sealed by an elastomer or rubber-like compound which is squeezed into the gaps for the purpose of blocking a leakage path. However, in high temperature environments, such rubber-like seals have a propensity to fail as a result of being exposed to temperatures which exceed the thermal limits of the seal.
Thus, a need is seen for a seal which will effectively reduce blade-to-blade and blade-to-disk leakage in a compressor of a gas turbine engine.